1. Field of the Invention
The present invention relates to tiltable-rotatable circular-table devices used as attachment devices for machine tools. In particular, the present invention relates to a tiltable-rotatable circular-table device including a main frame; a tiltable table having tilting shafts via which the tiltable table is axially supported on the main frame; a circular table rotatably disposed on the tiltable table; a tilt-driving motor which is disposed in the main frame and is provided for tilting the tiltable table via the tilting shafts; a rotary-driving motor which is fixed to the tiltable table and is provided for rotating the circular table; a motor cover which is fixed to the main frame and is provided for housing the rotary-driving motor; and cables connected with the rotary-driving motor.
2. Description of the Related Art
In a typical tiltable-rotatable circular-table device, when a workpiece is loaded onto a machine tool so as to be processed on the circular table, the circular table is rotated to a desired angle in order to index the rotational angle of the workpiece. Moreover, the tiltable table supporting the circular table is tilted by rotating the tilting-shafts, which axially support the tiltable table, in order to index the tilting angle of the workpiece. The rotation of the circular table to a desired angle is performed by the rotary-driving motor linked with the circular table via, for example, gears. On the other hand, the tilting of the tiltable table, i.e. the rotation of the tiltable table about the tilting shafts, is performed by the tilt-driving motor linked with the tilting shafts via, for example, gears provided in the main frame.
In such a typical tiltable-rotatable circular-table device, the circular table and the rotary-driving motor are mechanically linked with each other. For this reason, like the circular table, the rotary-driving motor is also supported by the tiltable table and is axially aligned with the tilting shafts of the tiltable table. Consequently, when the tiltable table is rotated about the tilting shafts so as to tilt the tiltable table, the rotary-driving motor is concurrently rotated about the same axis. In this case, cables, for example, which are connected with the rotary-driving motor to supply power to the rotary-driving motor, are also rotated with the rotary-driving motor about the same axis, and are thus thrown around in a disorderly manner around the rotary-driving motor. This is problematic in that the cables may hit the peripheral devices and units, causing the cables or the peripheral devices to break.
Japanese Unexamined Patent Application Publication No. 2002-273630 (claims, etc.) discloses a tiltable-rotatable circular-table device for solving such a problem. According to this tiltable-rotatable circular-table device, a motor, which rotates concurrently with the tilting of a table, and cables connected to the motor are housed inside a cover fixed to a main frame. Moreover, the cover also houses a belt-like resiliently-deformable cable-guide along which the cables are disposed. One end of the cable guide is fixed to the cover, and the cable guide itself can be expanded and retracted in response to the rotation of the motor. Furthermore, according to such a tiltable-rotatable circular-table device, since the movement of the cables around the motor in response to the rotation of the motor takes place strictly inside the cover, the cables are prevented from coming into contact with, for example, peripheral units. Moreover, the constant movement of the cables due to the cable guide prevents the cables from, for example, wearing and bending in the cover. Accordingly, this prevents the cables from, for example, breaking when moving inside the cover without having to increase the size of the cover.
According to the tiltable-rotatable circular-table device of Japanese Unexamined Patent Application Publication No. 2002-273630, the cable guide is formed of a resiliently-deformable belt-like plate, and such a plate can be deformed into a substantially cylindrical shape that can wrap around the periphery of the motor. Moreover, the resiliently-deformable plate can be deformed in a manner such that the diameter of the cylinder can be expanded and retracted in response to the rotation of the motor. In other words, when the motor is rotating, the diameter of the cylinder formed by the resiliently-deformable plate can be retracted against the resilient force of the plate or can be expanded with the restoring force of the plate.
According to such a cable guide, the resiliently-deformable plate is frequently deformed against its resilient force in a repetitive manner for every index operation of the tilting angle of a workpiece, i.e. every rotation of the tiltable table. For this reason, the plate is easily deteriorated and cannot be used for an extended period of time. This is problematic in view of the durability of the cable guide. Moreover, since such deterioration may lead to a lower resilient force and restoring force of the plate, the expansion and retraction of the diameter of the cylindrical plate cannot properly respond to the rotation of the motor. This may cause the plate to bend, such that the cable guide cannot properly fulfill its function. In the long run, this may cause the cables to break.
Furthermore, in such a cable guide, when the tiltable table is to be rotated in a direction in which the cables wrap around the periphery of the motor, the tilt-driving motor must rotate the tiltable table against the resilient force of the cable guide. This increases the load applied to the tilt-driving motor and a drive-transmission mechanism for the motor including, for example, gears, and may thus cause these elements to break at an earlier stage.